Now that fibre optic systems are becoming popular, in many instances replacing electronic transmission and signal processing systems, it has become necessary to facilitate the transition of system components from the laboratory to mass manufacturing.
The printed circuit board (PCB) has become over the years the primary vehicle for supporting electronic circuit components such as integrated circuits, capacitors, resistors and potentiometers. A particular class of the latter are now of particular importance, namely, the miniature trimming potentiometers popularly known as "trimpots". These permit a PCB adjustment after manufacturing by compensate for fixed component tolerances and/or to vary circuit attenuation in signal paths.
No reasonably close equivalent to the trimpot exists in optical components. While excellent variable optical attenuators (VOATs) are commercially available, with high setting accuracy, minimal reflexion and so on, they are suitable more for either the laboratory or only as a major (and expensive) component of a system. One such attenuator is made by Nippon Electric Company and having part number OD-8511. Another such VOAT is made by the present assignee and having part number VOAT 5000; it measures 10 cm.times.13 cm.times.18 cm and weighs one kilogram.